rajeshmarndi
New Member
how does the lower wing AOA increases to the sideslip relative air and level the flight?
dihedral and swept back lateral stability
- Thread starter rajeshmarndi
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pwapilot
Well-Known Member
The sideslip induces a component of relative wind perpendicular to the longitudinal axis. If you look at a projection of this component onto both the lowered and raised wings, you will see that there is an upward component of relative wind on the lowered wing (and an induced downward component on the raised wing) by virtue of the dihedral angle. When you add this upward component due to the sideslip to the relative wind due to just the forward motion, you will find that the AOA on the lowered wing is increased. This of course causes the increase in lift on that wing and a corresponding rolling moment.
Take a look at p.475 here (http://books.google.com/books?id=6-_iGbJHM-8C&printsec=frontcover#v=onepage&q&f=false) for one of the diagrams useful in visualizing this. You might want to also draw out the vector additions in the other two planes to get the complete picture. I can diagram this if it would help.
It's a similar deal for sweepback. If you project the sideslip component onto each wing, you will see that the lowered wing gets a "boost" in relative wind perpendicular to its leading edge, causing an increase in lift on that wing.
Mike
Take a look at p.475 here (http://books.google.com/books?id=6-_iGbJHM-8C&printsec=frontcover#v=onepage&q&f=false) for one of the diagrams useful in visualizing this. You might want to also draw out the vector additions in the other two planes to get the complete picture. I can diagram this if it would help.
It's a similar deal for sweepback. If you project the sideslip component onto each wing, you will see that the lowered wing gets a "boost" in relative wind perpendicular to its leading edge, causing an increase in lift on that wing.
Mike
rajeshmarndi
New Member
it seem it is due to the air strike that raises the down wing and not due to differential pressure as it is the case when the relative air is from the front. Also the width exposed to the relative sideslip is very much less and do not get downwash.
pwapilot
Well-Known Member
Thinking about air striking a surface is almost never a good way to think about aerodynamic flows. At least at the macroscopic level, air flows around surfaces, not onto/perpendicular to them. The additional aerodynamic force due to dihedral is indeed due to a pressure differential (the higher effective AOA causes the differential to increase).